Porsche has stopped deliveries of one of the fastest versions of its 911 sports car after two of them caught fire, the German automaker said.

Engineers at Porsche's Stuttgart-based headquarters are examining the remains of the gutted 911 GT3 models used in Switzerland and Italy to determine the cause of the fires, a spokesman said, confirming a report on German newswire dpa.

The Volkswagen-owned car maker expects to conclude the investigation this week, the spokesman said, adding that Porsche had this year delivered 322 of the 911 GT3 models, which start at €137,000.

The recall to rectify potentially faulty engines affects 785 cars worldwide, not all of which have been delivered to customers yet. The new 911 GT3 – which is based on the regular 991 generation of the iconic Porsche 911 that is the most famous Porsche model – only went on sale late 2013.

The GT3 is one of almost 20 911 models that are offered throughout the model's lifespan and has modifications to make it faster on the race track.